types of numbers

• Integers are whole numbers (both positive and negative, including zero). Examples include -2,-1, 0, 1, 2. So a negative integer is a negative whole number, such as -3, -10 or -23. Natural numbers are positive integers.
• A rational number is a number which can be written as a fraction where numerator and denominator are integers (where the top and bottom of the fraction are whole numbers). For example 1/2, 4, 1.75 (=7/4).
• Irrational numbers are numbers which cannot be written as fractions, such as pi and √2. In decimal form these numbers go on forever and the same pattern of digits are not repeated.
• Square numbers are numbers which can be obtained by multiplying another number by itself. E.g. 36 is a square number because it is 6 x 6
• Surds are numbers left written as √n , where n is positive but not a square number. E.g. √2
• Prime numbers are numbers above 1 which cannot be divided by anything (other than 1 and itself) to give an integer. The first 8 prime numbers are: 2, 3, 5, 7, 11, 13, 17, 19.
• Real numbers are all the numbers which you will have come across (i.e. all the rational and irrational numbers). All real numbers can be written in decimal form (such as 3.165).
• A factor (or divisor) of a number is a number which will divide into your number exactly. So you can divide a number by one of its factors and you won't be left with a remainder. For example, 3 is a factor of 6 because you can divide 6 by 3 and you won't be left with a remainder (you get 2).